The TomTom Runner Cardio and Multi-Sport Cardio GPS watches both include a heart rate monitor built into the strap that uses an optical sensor which shines light through the skin to detect changes in blood flow. It means athletes monitoring their physical condition during training no longer need to wear a chest strap that's wirelessly synced to their watch.

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Like the original TomTom Runner and Multi-Sport, the Cardio watches use QuickGPSFix to track a wearer's distance and speeds, but from our previous testing it can be finicky and slow to lock onto your location. However, as far as GPS-equipped watches go, the waterproof Cardios manage to keep a slim lightweight profile, thanks mostly to the use of a four-way controller on the strap that keeps the display free of buttons.

The updated Cardio versions of the TomTom Runner and Multi-Sport are available today for $270 and $300 respectively, which is about a $100 more than their predecessors. But it means there's less hardware to wrangle while out on a run, which make it very much worth the extra cash. [TomTom via Ubergizmo]